1 /* SPDX-License-Identifier: GPL-2.0 */ 2 #ifndef _ASM_X86_ALTERNATIVE_H 3 #define _ASM_X86_ALTERNATIVE_H 4 5 #include <linux/types.h> 6 #include <linux/stringify.h> 7 #include <linux/objtool.h> 8 #include <asm/asm.h> 9 #include <asm/bug.h> 10 11 #define ALT_FLAGS_SHIFT 16 12 13 #define ALT_FLAG_NOT (1 << 0) 14 #define ALT_NOT(feature) ((ALT_FLAG_NOT << ALT_FLAGS_SHIFT) | (feature)) 15 #define ALT_FLAG_DIRECT_CALL (1 << 1) 16 #define ALT_DIRECT_CALL(feature) ((ALT_FLAG_DIRECT_CALL << ALT_FLAGS_SHIFT) | (feature)) 17 #define ALT_CALL_ALWAYS ALT_DIRECT_CALL(X86_FEATURE_ALWAYS) 18 19 #ifndef __ASSEMBLER__ 20 21 #include <linux/stddef.h> 22 23 #ifdef CONFIG_SMP 24 #define LOCK_PREFIX "lock " 25 #else 26 #define LOCK_PREFIX "" 27 #endif 28 29 /* 30 * The patching flags are part of the upper bits of the @ft_flags parameter when 31 * specifying them. The split is currently like this: 32 * 33 * [31... flags ...16][15... CPUID feature bit ...0] 34 * 35 * but since this is all hidden in the macros argument being split, those fields can be 36 * extended in the future to fit in a u64 or however the need arises. 37 */ 38 struct alt_instr { 39 s32 instr_offset; /* original instruction */ 40 s32 repl_offset; /* offset to replacement instruction */ 41 42 union { 43 struct { 44 u32 cpuid: 16; /* CPUID bit set for replacement */ 45 u32 flags: 16; /* patching control flags */ 46 }; 47 u32 ft_flags; 48 }; 49 50 u8 instrlen; /* length of original instruction */ 51 u8 replacementlen; /* length of new instruction */ 52 } __packed; 53 54 extern struct alt_instr __alt_instructions[], __alt_instructions_end[]; 55 56 extern s32 __retpoline_sites[], __retpoline_sites_end[]; 57 extern s32 __return_sites[], __return_sites_end[]; 58 extern s32 __cfi_sites[], __cfi_sites_end[]; 59 extern s32 __ibt_endbr_seal[], __ibt_endbr_seal_end[]; 60 61 /* 62 * Debug flag that can be tested to see whether alternative 63 * instructions were patched in already: 64 */ 65 extern int alternatives_patched; 66 67 extern void alternative_instructions(void); 68 extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end); 69 extern void apply_retpolines(s32 *start, s32 *end); 70 extern void apply_returns(s32 *start, s32 *end); 71 extern void apply_seal_endbr(s32 *start, s32 *end); 72 extern void apply_fineibt(s32 *start_retpoline, s32 *end_retpoine, 73 s32 *start_cfi, s32 *end_cfi); 74 75 struct module; 76 77 struct callthunk_sites { 78 s32 *call_start, *call_end; 79 }; 80 81 #ifdef CONFIG_CALL_THUNKS 82 extern void callthunks_patch_builtin_calls(void); 83 extern void callthunks_patch_module_calls(struct callthunk_sites *sites, 84 struct module *mod); 85 extern void *callthunks_translate_call_dest(void *dest); 86 extern int x86_call_depth_emit_accounting(u8 **pprog, void *func, void *ip); 87 #else 88 static __always_inline void callthunks_patch_builtin_calls(void) {} 89 static __always_inline void 90 callthunks_patch_module_calls(struct callthunk_sites *sites, 91 struct module *mod) {} 92 static __always_inline void *callthunks_translate_call_dest(void *dest) 93 { 94 return dest; 95 } 96 static __always_inline int x86_call_depth_emit_accounting(u8 **pprog, 97 void *func, void *ip) 98 { 99 return 0; 100 } 101 #endif 102 103 #ifdef CONFIG_MITIGATION_ITS 104 extern void its_init_mod(struct module *mod); 105 extern void its_fini_mod(struct module *mod); 106 extern void its_free_mod(struct module *mod); 107 extern u8 *its_static_thunk(int reg); 108 #else /* CONFIG_MITIGATION_ITS */ 109 static inline void its_init_mod(struct module *mod) { } 110 static inline void its_fini_mod(struct module *mod) { } 111 static inline void its_free_mod(struct module *mod) { } 112 static inline u8 *its_static_thunk(int reg) 113 { 114 WARN_ONCE(1, "ITS not compiled in"); 115 116 return NULL; 117 } 118 #endif 119 120 #if defined(CONFIG_MITIGATION_RETHUNK) && defined(CONFIG_OBJTOOL) 121 extern bool cpu_wants_rethunk(void); 122 extern bool cpu_wants_rethunk_at(void *addr); 123 #else 124 static __always_inline bool cpu_wants_rethunk(void) 125 { 126 return false; 127 } 128 static __always_inline bool cpu_wants_rethunk_at(void *addr) 129 { 130 return false; 131 } 132 #endif 133 134 #define ALT_CALL_INSTR "call BUG_func" 135 136 #define alt_slen "772b-771b" 137 #define alt_total_slen "773b-771b" 138 #define alt_rlen "775f-774f" 139 140 #define OLDINSTR(oldinstr) \ 141 "# ALT: oldinstr\n" \ 142 "771:\n\t" oldinstr "\n772:\n" \ 143 "# ALT: padding\n" \ 144 ".skip -(((" alt_rlen ")-(" alt_slen ")) > 0) * " \ 145 "((" alt_rlen ")-(" alt_slen ")),0x90\n" \ 146 "773:\n" 147 148 #define ALTINSTR_ENTRY(ft_flags) \ 149 ".pushsection .altinstructions, \"aM\", @progbits, " \ 150 __stringify(ALT_INSTR_SIZE) "\n" \ 151 " .long 771b - .\n" /* label */ \ 152 " .long 774f - .\n" /* new instruction */ \ 153 " .4byte " __stringify(ft_flags) "\n" /* feature + flags */ \ 154 " .byte " alt_total_slen "\n" /* source len */ \ 155 " .byte " alt_rlen "\n" /* replacement len */ \ 156 ".popsection\n" 157 158 #define ALTINSTR_REPLACEMENT(newinstr) /* replacement */ \ 159 ".pushsection .altinstr_replacement, \"ax\"\n" \ 160 ANNOTATE_DATA_SPECIAL "\n" \ 161 "# ALT: replacement\n" \ 162 "774:\n\t" newinstr "\n775:\n" \ 163 ".popsection\n" 164 165 /* alternative assembly primitive: */ 166 #define ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 167 OLDINSTR(oldinstr) \ 168 ALTINSTR_ENTRY(ft_flags) \ 169 ALTINSTR_REPLACEMENT(newinstr) 170 171 #define ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \ 172 ALTERNATIVE(ALTERNATIVE(oldinstr, newinstr1, ft_flags1), newinstr2, ft_flags2) 173 174 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 175 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \ 176 ALTERNATIVE_2(oldinstr, newinstr_no, X86_FEATURE_ALWAYS, newinstr_yes, ft_flags) 177 178 #define ALTERNATIVE_3(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, \ 179 newinstr3, ft_flags3) \ 180 ALTERNATIVE(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2), \ 181 newinstr3, ft_flags3) 182 183 /* 184 * Alternative instructions for different CPU types or capabilities. 185 * 186 * This allows to use optimized instructions even on generic binary 187 * kernels. 188 * 189 * length of oldinstr must be longer or equal the length of newinstr 190 * It can be padded with nops as needed. 191 * 192 * For non barrier like inlines please define new variants 193 * without volatile and memory clobber. 194 */ 195 #define alternative(oldinstr, newinstr, ft_flags) \ 196 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) : : : "memory") 197 198 #define alternative_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) \ 199 asm_inline volatile(ALTERNATIVE_2(oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2) ::: "memory") 200 201 /* 202 * Alternative inline assembly with input. 203 * 204 * Peculiarities: 205 * No memory clobber here. 206 * Argument numbers start with 1. 207 * Leaving an unused argument 0 to keep API compatibility. 208 */ 209 #define alternative_input(oldinstr, newinstr, ft_flags, input...) \ 210 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 211 : : "i" (0), ## input) 212 213 /* Like alternative_input, but with a single output argument */ 214 #define alternative_io(oldinstr, newinstr, ft_flags, output, input...) \ 215 asm_inline volatile(ALTERNATIVE(oldinstr, newinstr, ft_flags) \ 216 : output : "i" (0), ## input) 217 218 /* 219 * Like alternative_io, but for replacing a direct call with another one. 220 * 221 * Use the %c operand modifier which is the generic way to print a bare 222 * constant expression with all syntax-specific punctuation omitted. %P 223 * is the x86-specific variant which can handle constants too, for 224 * historical reasons, but it should be used primarily for PIC 225 * references: i.e., if used for a function, it would add the PLT 226 * suffix. 227 */ 228 #define alternative_call(oldfunc, newfunc, ft_flags, output, input, clobbers...) \ 229 asm_inline volatile(ALTERNATIVE("call %c[old]", "call %c[new]", ft_flags) \ 230 : ALT_OUTPUT_SP(output) \ 231 : [old] "i" (oldfunc), [new] "i" (newfunc) \ 232 COMMA(input) \ 233 : clobbers) 234 235 /* 236 * Like alternative_call, but there are two features and respective functions. 237 * If CPU has feature2, function2 is used. 238 * Otherwise, if CPU has feature1, function1 is used. 239 * Otherwise, old function is used. 240 */ 241 #define alternative_call_2(oldfunc, newfunc1, ft_flags1, newfunc2, ft_flags2, \ 242 output, input, clobbers...) \ 243 asm_inline volatile(ALTERNATIVE_2("call %c[old]", "call %c[new1]", ft_flags1, \ 244 "call %c[new2]", ft_flags2) \ 245 : ALT_OUTPUT_SP(output) \ 246 : [old] "i" (oldfunc), [new1] "i" (newfunc1), \ 247 [new2] "i" (newfunc2) \ 248 COMMA(input) \ 249 : clobbers) 250 251 #define ALT_OUTPUT_SP(...) ASM_CALL_CONSTRAINT, ## __VA_ARGS__ 252 253 /* Macro for creating assembler functions avoiding any C magic. */ 254 #define DEFINE_ASM_FUNC(func, instr, sec) \ 255 asm (".pushsection " #sec ", \"ax\"\n" \ 256 ".global " #func "\n\t" \ 257 ".type " #func ", @function\n\t" \ 258 ASM_FUNC_ALIGN "\n" \ 259 #func ":\n\t" \ 260 ASM_ENDBR \ 261 instr "\n\t" \ 262 ASM_RET \ 263 ".size " #func ", . - " #func "\n\t" \ 264 ".popsection") 265 266 void BUG_func(void); 267 void nop_func(void); 268 269 #else /* __ASSEMBLER__ */ 270 271 .macro LOCK_PREFIX 272 #ifdef CONFIG_SMP 273 lock 274 #endif 275 .endm 276 277 /* 278 * Issue one struct alt_instr descriptor entry (need to put it into 279 * the section .altinstructions, see below). This entry contains 280 * enough information for the alternatives patching code to patch an 281 * instruction. See apply_alternatives(). 282 */ 283 .macro altinstr_entry orig alt ft_flags orig_len alt_len 284 .long \orig - . 285 .long \alt - . 286 .4byte \ft_flags 287 .byte \orig_len 288 .byte \alt_len 289 .endm 290 291 .macro ALT_CALL_INSTR 292 call BUG_func 293 .endm 294 295 /* 296 * Define an alternative between two instructions. If @feature is 297 * present, early code in apply_alternatives() replaces @oldinstr with 298 * @newinstr. ".skip" directive takes care of proper instruction padding 299 * in case @newinstr is longer than @oldinstr. 300 */ 301 #define __ALTERNATIVE(oldinst, newinst, flag) \ 302 740: \ 303 oldinst ; \ 304 741: \ 305 .skip -(((744f-743f)-(741b-740b)) > 0) * ((744f-743f)-(741b-740b)),0x90 ;\ 306 742: \ 307 .pushsection .altinstructions, "aM", @progbits, ALT_INSTR_SIZE ;\ 308 altinstr_entry 740b,743f,flag,742b-740b,744f-743f ; \ 309 .popsection ; \ 310 .pushsection .altinstr_replacement,"ax" ; \ 311 743: \ 312 ANNOTATE_DATA_SPECIAL ; \ 313 newinst ; \ 314 744: \ 315 .popsection ; 316 317 .macro ALTERNATIVE oldinstr, newinstr, ft_flags 318 __ALTERNATIVE(\oldinstr, \newinstr, \ft_flags) 319 .endm 320 321 /* 322 * Same as ALTERNATIVE macro above but for two alternatives. If CPU 323 * has @feature1, it replaces @oldinstr with @newinstr1. If CPU has 324 * @feature2, it replaces @oldinstr with @feature2. 325 */ 326 .macro ALTERNATIVE_2 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2 327 __ALTERNATIVE(__ALTERNATIVE(\oldinstr, \newinstr1, \ft_flags1), 328 \newinstr2, \ft_flags2) 329 .endm 330 331 .macro ALTERNATIVE_3 oldinstr, newinstr1, ft_flags1, newinstr2, ft_flags2, newinstr3, ft_flags3 332 __ALTERNATIVE(ALTERNATIVE_2(\oldinstr, \newinstr1, \ft_flags1, \newinstr2, \ft_flags2), 333 \newinstr3, \ft_flags3) 334 .endm 335 336 /* If @feature is set, patch in @newinstr_yes, otherwise @newinstr_no. */ 337 #define ALTERNATIVE_TERNARY(oldinstr, ft_flags, newinstr_yes, newinstr_no) \ 338 ALTERNATIVE_2 oldinstr, newinstr_no, X86_FEATURE_ALWAYS, \ 339 newinstr_yes, ft_flags 340 341 #endif /* __ASSEMBLER__ */ 342 343 #endif /* _ASM_X86_ALTERNATIVE_H */ 344